Cohoes is a brick city built around a waterfall — the Mohawk drops over the falls and swings into the Hudson, and the mill walls above it keep the roar close. Trail Based Tree Service works the hill streets and the island yards below, pruning silver maples that lean over the sidewalks, trimming limbs off the slate roofs and the lines threaded between them. Removals happen in close quarters, roped down between a driveway and a neighbor's porch rail. When the river wind comes up in March and lays deadwood across the yards, the storm damage cleanup carries it off and leaves the grass combed. The best hour is early, before the traffic, when the falls are the loudest thing in town.